Spark plug



, R. H. DEvAUx SPARK PLUG Sept. 1, 1953 Filed Jan. 4, 1950 INVENToR Raymond Henri evaax BY j /EL/.zv/ www Patented Sept. 1, 1953 UNITED STATES PATENT GFFICE Application January 4, 1950, Serial No. 136,803 In France January 1I), 1949 (Cl. 12S-169) 1 Claim.

This invention relates to improvements in spark plugs.

According to the invention, the electrode which is integral with the body of the spark plug is a compound electr-ode, that is to say made of at least two layers of points or crowns at whose level the arc can strike between the said integral or solid electrode and the central electrode. It is a feature of the invention that one ci the layers is in Contact with or in the immediate proximity of the central insulating block of the plug. Due to this arrangement, when the spark plug funetions normally, sparks occur between the central electrode and the points or crowns which are remote from the central insulating block, in manner of a normal type of spark plug. After prolonged use, a carbon deposit forms on the insulator and the arc now strikes between the central electrode and the points or crowns which are adjacent or touch the central insulating block, the said arc then being carried by the insulator according to one of the characteristic dispositions of the plug which formed the subject of a prior United States patent application in the name of the same applicant, led on January 8, 1948, un der Serial No. 1,162, for Sparkplug for explosion engines. Experiment shows that the carried arc not only burns the carbon the deposit of which, on the insulator, had produced the striking, but also the dirt liable to impede the strilping of the arc between the central electrode and the points or crowns different I" those that are in contact with or in the immediate proximity of the insulator.

Under these conditions, after a short time, the normal functioning of the plug is resumed, that is to say the arc again strikes between the centrai electrode and the point or points or crowns of the solid electrode which are not concerned in i producing the carried arc.

The improved spark plug according to the invention is shown by way of example in the accompanying drawings, in which:

Figure 1 is a longitudinal section of the plug.

Figures 3 and 5 are partial views in longitudinal sections, showing two further embodiments of the invention.

Figures 2, 4 and 6 are plan views, from below, respectively corresponding to Figures l, 3 and 5.

This solid electrode (Figs. 1 and 2) is formed by two layers of crowns, one of which, I, ensures the normal working of the plug, and the other of which, 2, is set up adjacent the insulating block 3. When working normally, the arc strikes between the points I and the central electrode 4. When the consequence of the carbon deposited on the surface of the insulating block 3, the surface of this block becomes more conductive, the carried arc establishes itself between the layer 2 and the central electrode t. This arc consumes the carbon thus deposited on it and after a brief pause, the normal working is restored by the arc against striking between the crown l and the central electrode.

Figures 3 and 4 show a modified form of the invention in which the electrode, consisting of two sets of points I and 2, has the points I, for normal working, arranged in such a way that the arc strikes in a vertical direction, that is to say, parallel to the axis of the central electrode instead oi striking, as in the case of Figures 1 and 2, in a plane perpendicular to this axis.

Figures 5 and 6 a modified electrode having three layers, one of which I is the type represented in Figures 3 and 4, a second la, of the type represented in Figures 1 and 2, while the third layer 2, is concerned with the carried arc in the conditions described above.

What I claim is:

A self-cleansing compound sparkplug which comprises a central electrode surrounded by a mass of insulation; said central electrode projecting below the lower extremity of said insulation; a mass electrode positioned exterior to said insulation; said mass electrode having at its lower portion a sparking crown comprised of three tiers; the lowermost of said tiers being below the lower end of the central electrode; the middle of said tiers being positioned above said lower end or" the central electrode; the uppermost of said tiers being positioned in close proximity to the lower portion of the insulation; the shortest distance between said lowermost tier and the central electrode being slightly less than. the shortest distance between the uppermost tier and the central electrode.

RAYMOND HENRI DEVAUX.

References Cited in the ille of this patent UNITED STATES PATENTS Number Name Date 1,554,271 Fye Sept. 22, 1925 1,962,669 Parkin June 12, 1934 2,028,971 Falor Jan. 28, 1936 2,150,728 Nowosielski Mar. 14, 1939 FOREIGN PATENTS Number Country Date 308,472 Great Britain Mar. 28, 1929 498,541 Great Britain Jan. 10, 1939 

